(1) Field of the Invention
The present invention relates generally to an apparatus and method for dressing grinding tools. This invention more particularly relates to a tool (i.e., a burr) and a method for dressing (also referred to as sharpening) pulpstone grinding tools used for the mechanical preparation of wood pulp. The tool of this invention advantageously may provide for both improved quality wood pulp and for a longer life pulpstone grinding tool.
(2) Background Information
The use of pulpstone grinding tools to grind wood (e.g., in the form of tree trunks or alternately in the form of chips) into fibrous wood pulp for the paper industry is well known. A typical pulpstone grinding tool is cylindrical in shape, and relatively large and complex, for example, including a diameter from about 120 to about 190 cm or more (about 48 to 75 inches) and a length from about 70 to about 230 cm or more (i.e., about 28 to 90 inches). A conventional pulpstone grinding tool typically includes a plurality of abrasive segments assembled about a cylindrical concrete core (see, for example, U.S. Pat. No. 5,243,789 to Bacic). The segments generally include a mixture of abrasive grains and bond material (e.g., ceramic, vitrified, or cement bond) pressed together into a desired shape.
In order to improve the grinding performance of conventional pulpstone grinding tools, the grinding surface thereof is typically dressed (also referred to as sharpened). Dressing generally includes applying a tool, referred to herein as a burr, to the pulpstone""s grinding surface. For example, a burr may be rolled over the surface of the pulpstone grinding tool, under sufficient pressure to impart a pattern of impressions to the surface. A commercially available spiral burr (e.g., the 6xc3x9728 manufactured by Norton Canada, Inc., Hamilton, Ontario, Canada) may be used to impart a pattern of grooves and lands into the surface of the pulpstone grinding tool, as discussed in more detail hereinbelow.
The features of a typical burr affect the pattern in the grinding surface of a pulpstone grinding tool and therefore, affect the properties of the wood pulp produced thereby. For example, the fiber length of the wood pulp tends to be inversely related to the lead angle of a spiral burr used to dress the pulpstone grinding tool. Further, the features of the burr may impact the life of a pulpstone grinding tool and, therefore, may have a significant effect on the final cost of wood pulp. Therefore an improved dressing tool and/or an improved method for dressing the surface of a pulpstone grinding tool may provide for improved quality and/or reduced cost of wood pulp and may therefore be highly desirable by the paper and other wood pulp producing industries.
One aspect of the present invention includes a burr adapted for dressing a grinding surface of a grinding tool. The burr includes a cylindrical body portion having an outer surface, a plurality of teeth protruding radially outward from the outer surface, and at least one annular channel disposed in the outer surface. In one variation of this aspect, the burr is useful for dressing a grinding surface of a pulpstone grinding tool adapted for mechanical preparation of wood pulp.
In other aspect, this invention includes a burr for dressing a grinding surface of a pulpstone grinding tool adapted for mechanical preparation of wood pulp. The burr includes a cylindrical body portion having an outer surface, a length (axial dimension), and a longitudinal axis. The burr further includes a plurality of teeth extending radially outward from the outer surface and at least one annular channel disposed in the outer surface. The burr is useful for dressing a grinding surface of a pulpstone grinding tool adapted for mechanical preparation of wood pulp.
In still another aspect, this invention includes a method of fabricating a burr useful for dressing a grinding surface of a pulpstone grinding tool adapted for mechanical preparation of wood pulp. The method includes providing a cylindrical body portion having an outer surface, forming a plurality of teeth in the outer surface of the cylindrical body portion, and forming at least one annular channel in the outer surface of the cylindrical body portion.
In yet another aspect, this invention includes a method of dressing a grinding surface of a pulpstone grinding tool adapted for mechanical preparation of wood pulp. The method includes providing a burr including a cylindrical body portion having an outer surface, a plurality of teeth disposed on and protruding from the outer surface, and at least one annular channel disposed in the outer surface. The method further includes rotatably mounting the burr on an assembly adapted to traverse the length of the pulpstone grinding tool, pressing the burr into contact with the grinding surface of the pulpstone grinding tool, rotating the pulpstone grinding tool, so that the burr rolls over the grinding surface thereof, and traversing the burr along the length of the pulpstone grinding tool.